Detección del determinante genético (cfiA) de la resistencia a carbapenems y su entorno molecular en aislamientos clínicos de bacilos gram negativos anaerobios
Among Bacteroides fragilis group, Bacteroides fragilis constitutes the most frequently recovered specie in clinical specimens, partially because it is the most virulent specie of the group.\nMost of B. fragilis isolates result resistant to ?-lactam antibiotics, except carbapenems, being production o...
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| Formato: | Tesis de maestría acceptedVersion |
| Lenguaje: | Español |
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Facultad de Farmacia y Bioquímica
2016
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=afamaster&cl=CL1&d=HWA_1918 http://repositoriouba.sisbi.uba.ar/gsdl/collect/afamaster/index/assoc/HWA_1918.dir/1918.PDF |
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| Sumario: | Among Bacteroides fragilis group, Bacteroides fragilis constitutes the most frequently recovered specie in clinical specimens, partially because it is the most virulent specie of the group.\nMost of B. fragilis isolates result resistant to ?-lactam antibiotics, except carbapenems, being production of ?-lactamases the principal resistance mechanism. Three different ?-lactamases have been described in B. fragilis: - CepA, an endogenous cephalosporinase conferring resistance to the majority of the ?-lactam antibiotics with the exception of cephamycins,and carbapenems, and that is inhibited by ?-lactamase inhibitors. - CfxA which confers resistance to cephaloridine, cefoxitin, and others ?-lactams with the exception of imipenem. And CfiA, a metallo-?-lactamase which is active against penicilins, cephalosporins, including cephamycins, and carbapenems. CfiA is neither inhibited by clavulanic acid nor sulbactam. EDTA is a good inhibitor of CfiA and its activity could be recovered by the addition of Zn2+.\nThe activity of antimicrobial agents against Bacteroides fragilis group isolates remained unchanged through different survey studies performed in our country. However, in a surveillance study conducted between 2006 and 2009, 3 clinical isolates of gram negative rods of this group displaying high level resistance (CIM?32 ?g/ml) to carbapenems were detected.\nThis finding was the first report in our country in isolates of B. fragilis from clinical materials.\nThe presence of a metallo-?-lactamase in those isolates was suspected from inhibition tests with EDTA. The overall objective of this study was to analyze the presence of cfiA resistance marker in isolates recovered during the study previously mentioned and to analyze the genetic environment of this marker.\nThis is the first study in Argentina, in which 7 isolates of B. fragilis carring cfiA strains are informed. Three of them correspond to those isolates that showed high level resistance to carbapenems (CIM?32 ?g/ml). In 2/3 CfiA13 was identify and its coding gene was associated to an IS corresponding to IS1380 family, IS942 group. In the other resistant isolate CfiA4 was identified and its coding genes was associated to an IS belonging to family IS21 family.\nIn the 4 imipenem susceptible strains CfiA4, CfiA2 and two new variants related to CfiA4 and CfiA13 were identified. No IS elements were found upstream their coding genes. Promoter sequences -10 and -35 adjacent upstream cfiA2 were only identified in the doripenem intermediate isolate |
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